Methylmethacrylate monomer produces direct relaxation of vascular smooth muscle in vitro

Methylmethacrylate bone cement is associated with severe hypotensive reactions during surgery and anesthesia. The purpose of this in vitro study was to determine if methylmethacrylate monomer could produce hypotension by acting directly on vascular smooth muscle. Segments of human saphenous vein or rabbit thoracic aorta were cut into rings. The rings were mounted in isolated tissue chambers in order to measure isometric tension development. Methylmethacrylate monomer (methylmethacrylic acid ester) produced direct relaxation of venous or aortic rings preconstricted with either potassium ion or noradrenaline. The relaxation was concentration-dependent, occurring at concentrations from 10(-3) to 10(-1) M. The relaxation of rabbit aortic rings (preconstricted with noradrenaline) was unaffected by pre-treatment with atropine, propranolol, cimetidine, indomethacin, or methylene blue. Endothelial stripping with Triton X-100, sufficient to completely abolish acetylcholine-induced relaxation, also had little effect on methylmethacrylate-induced relaxation. Methylmethacrylate produced direct relaxation of rabbit aortic rings constricted with either potassium or noradrenaline in calcium-deficient media, and inhibited subsequent calcium-induced constriction. These results suggest that methylmethacrylate monomer may interfere with intracellular and extracellular calcium mobilization and excitation/contraction coupling in vascular smooth muscle. The direct relaxation of venous and arterial smooth muscle produced by methylmethacrylate monomer may contribute in part to the hypotension that can occur when acrylic bone cement is employed during orthopedic procedures.